1. Field of the Invention
This invention relates to a novel viologen derivative and a process for producing the same. Particularly it relates to a novel viologen derivative having at least one polymerizable vinyl group directly bonded to a viologen skeleton and a process for producing the same.
2. Description of the Prior Art
A viologen derivative easily conducts a reversible oxidation-reduction (redox) reaction under various conditions. It has attracted an attention because the reductant thereof is colored. It has been proposed to be used as photo- or electrochromic display materials, photoelectrochemical cell materials, mediators for redox reactions, various sensors and the like. For this reason, various derivatives and oligomers have been produced so far. Among them, a low molecular viologen derivative has disadvantages such as a short repetition life as well as a slow response and a short memory life when used as an display material. Further a short absorption wavelength has been pointed out as a drawback when used as a photochromic material or the like.
As a countermeasure for avoiding these drawbacks, it has been proposed to use various oligomers and polymers having a viologen group, which are divided roughly into those having a viologen group in a main chain (backbone) and those having a viologen group in a side chain (pendant). However although having a slightly increased stability in redox cycles the formers have disadvantages that an electron transfer rate is considerably lowered and, when used as a film, sufficient film properties are not obtainable. The latters have drawbacks that a stability is lowered, although it has an increased electron transfer rate.
On the other hand, a viologen monomer having a vinyl group has attracted an attention, because it is polymerized and can be modified in various manners. However the monomers which have been proposed until now have a spacer between a vinyl group and a viologen structure, and therefore they could not solve the above mentioned drawbacks.
Accordingly, an object of the present invention is to provide a novel viologen derivative which solve the above mentioned drawbacks and a process for producing the same.